Field of the Invention
The present invention relates to a bonding method.
Background Art
In recent years, products such as a mobile telephone, digital AV equipment, an IC card, and the like have been improved to have more sophisticated functions. This gives rise to an increase in the demand that semiconductor silicon chips (hereinafter, referred to as chips) provided in the products are downsized and thinned so that chips can be provided with higher density in a package. For example, for an integrated circuit in which a plurality of chips are provided in one package, such as a CSP (chip size package) or an MCP (multi-chip package), there is a demand that the chips be further thinned. In order to provide the chips with higher density in the package, it is necessary to thin the chips to a thickness in a range of 25 μm to 150 μm.
By a grinding process, semiconductor wafers (hereinafter, referred to as wafers) which serve as bases for the respective chips are thinned. However, this weakens the strength, and cracks or warpages are likely to be formed. In addition, the wafers weakened in strength through the thinning are difficult to be transported automatically and need to be transported manually. As can be understood from this, handling of the wafers is troublesome.
As a countermeasure, a wafer handling system is developed which adds strengths to the wafers. According to the wafer handling system, a plate called a support plate, which is made from glass, silicon, or hard plastic, or the like, is bonded to the wafers to be thinned so that the wafers are prevented from being cracked or warped.
Because the strength of the wafers can be secured by the wafer handling system, it is possible to automatically transport the wafers after the thinning process.
In the wafer handling system, the wafers and the support plate are bonded to each other by use of an adhesive tape, a thermoplastic resin, an adhesive composition, or the like. Then, the wafers to which the support plate is bonded are thinned. After this, the support plate is peeled off from a substrate before the wafers are diced. Specifically, in a case where the wafer and the support plate are bonded to each other with the use of the adhesive, the wafers are peeled off from the support plate by dissolving the adhesive.
JP-A-2002-192394 (publication date: Jul. 10, 2002) discloses a pressing method of inorganic substrates in which a set combined with a laminate material including an inorganic substrate formed of semiconductors or ceramics and an auxiliary material for laminating is installed between a pair of upper and lower heating plates heated to a predetermined temperature in a decompression press, and after the pair of heating plates is brought into contact with the combined set, at least, a low-pressure load, which is up to 0.05 MPa, is applied for 10 seconds or longer from the start of pressurization.